Current methods for diagnosing Alzheimer's disease are primarily via clinical evaluation of symptoms. Proposed methods are invasive, including assessment of amyloid beta (Aβ) and other substances in the cerebral spinal fluid, the blood or genetic markers, among others. Other methods of scanning the brain are expensive and not widely available, including brain scans via MRI and PET scanning, using molecules which bind to Aβ, tagged with radionucleotide markers. The presence of Aβ in neural tissue is recognized as indicative of Alzheimer's disease. There is a need for a readily available, objective, relatively inexpensive diagnostic for Alzheimer's disease with the potential to allow longitudinal quantification of disease progression, which is sensitive and specific and would enable earlier and more accurate diagnosis. Differential detection of Aβ in the neural tissue of the retina provides such a diagnostic.
Optical imaging is advantageous because it is relatively noninvasive and without the risk of radiation exposure. In diagnosing Alzheimer's disease, optical imaging of the brain has been proposed but this is most suitable for imaging through the thinner skull of rodent models of the disease, rather than through the human skull.
It would be advantageous to provide an optical method of imaging in the eye which would provide a differential diagnosis of Alzheimer's disease. Optical imaging in the eye has the advantage of scattering much less light than the brain with an optical window through the front of the eye, transparent to wavelengths in the visible and infrared. This allows the neural tissue at the rear of the eye, the neural retina, to be imaged. There is also an ongoing need to image the induction, the progression and the results of treatment of the disease in animal models of Alzheimer's disease, including but not limited to rodent models of Alzheimer's disease.